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Kinetics and Mechanism of the Reduction of Hexavalent Chromium to Less Toxic Materials on ZnO Nanostructured Surfaces: the Effect of Wavelength and Light Intensity on the Reaction Rate

Alyannezhadi, Mojtaba | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56742 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Moshfegh, Alireza; Naseri, Ameneh
  7. Abstract:
  8. Hexavalent chromium ion (Cr+6) is a very toxic type of heavy metal in industrial effluents which is not biodegradable and accumulates in the human body that can cause genetic mutations and cancer. The aim of this project is to investigate the effect of wavelength and intensity of appropriate light on the reaction rate of photocatalytic reduction of Cr+6 ion to less toxic materials. In this project, we first designed and constructed a photocatalytic reactor to investigate the effect of wavelength and intensity of incident light on the reaction rate. The home-made photocatalytic reactor consisted of 120 LEDs in 12 different wavelengths, which has ability to control the intensity and wavelength of incident light through a microcontroller and computer software. Upon installation and calibration, the maximum intensity of the light source measured at about 400 mW/cm2 at its focal point, which provides the possibility of examining a wide range of intensity. Fourier transform infrared (FTIR), diffuse reflectance spectroscopy (DRS), field effect scanning electron microscopy (FESEM) and x-ray photoelectron spectroscopy (XPS) methods are applied to determine properties of prepared photocatalysts. According to our FESEM image analysis, it was found that the nanofibers are well formed and are uniformly distributed in the entire photocatalyst. The average diameter of the annealed nanofibers was estimated at about 183 nanometers. The highest photocatalytic activity of the ZnO-C towards reduction of Cr+6 ion to less toxic materials was measured at 365 nm and its rate reached to Kapp=10.03 (% min-1)
  9. Keywords:
  10. Photo-Reactor ; Electrospun Nanofibers ; Hexavalent Chromium ; Zinc Oxide Nanostructures ; Photocatalytic Reduction

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